Sheets-sheet



April 28, 1953 M. H. GRAHAM 2,636,972

ALTERNATING CURRENT-DIRECT CURRENT FLATIRON Filed NOV. 24, 1948 2 SHEETS-SHEET l 2 lNVENTOR I5 MAURICE H. GRAHAM A T TORNE Y A ril 28, 1953 M. H. GRAHAM 2,63 72 ALTERNATING CURRENT-DIRECT CURRENT FLATIRON Filed Nov. 24, 1948 2 SHEETS-SHEET 2 INVENTOR MAURICE H. GRAHAM 7611-; C. ATTORNEY Patented Apr. 28, 1953 ALTERNATING CURRENT-DIRECT CURRENT FLATIRON Maurice H. Graham, Minneapolis, Minn., assignor to General. Mills, Inc., a. corporation of Delaware Application November 24, 1948, Serial No. 61,845

1.2 Claims.

The present invention relates to fiatirons and more particularly to a fiatiron which may be used selectively with both alternating current and direct current supplies.

The great majority of household appliances such as flatirons are designed for use with alternating current supplies because alternating cur-- rent predominates in household electrical systems. There are, however, a number of installations in which direct current is utilized. One such use of direct current is in hotels in major cities of the country. It is therefore desirable to provide a fiatiron and particularly a flatiron of the small or traveling type which may be utilized selectively on either alternating current or direct current as the case may be.

In alternating current flatirons of known construction, it is customary to provide a thermostatic switch which automatically cuts the heating element on and off to maintain the desired temperature at the soleplate of the iron. It is not practical to use such a thermostatic switch with a direct current supply because the making and breaking of the electrical circuit would involve considerable arcing at the contacts of the switch and would soon destroy these contacts and make the iron inoperative. While irons have been made in the past for use with direct current, it is necessary in such case that the wattage. of the heating element be kept low enough so that the element may be energized continuously without unnecessary or dangerous heating of the iron.

With the foregoing problems in mind, it is one object of the present invention to, provide a flatiron construction suitable for selective use with alternating current and direct current.

It is a further object to provide a llatiron construction in which a thermostatic switch incorporated in the circuit for alternating current operation.

It is a further object to provide means for cutting such a thermostatic switch out of the circuit when the fiatiron is to be used for direct current operation.

Still another object of the invention is the, provision of an auxiliary resistance which may be included in the heating element circuit for direct current operation in order to cut down the effective heating of the element during such use.

A still further object is the provision of suitable switch or control means for selective connection oi the parts in the desired relation for A. C. and D. C. operation.

Other objects and advantages of the invention will be apparent from the following specification in which a preferred embodiment of the invention is described.

In the drawings which form a part of this application, Figures 1, 2, and 3 constitute an exploded view of a fiatiron construction according to the present invention.

Figure 1 shows the handle and shell assembly together with details of the control switch.

Fig. 2 is a perspective view of the thermostatic switch mechanism, and

Fig. 3 is a perspective view of the soleplate and heating element of the iron.

The parts in the three figures are connected by wiring to show their operative relationship to each other.

Fig. 4 is an exploded view of a modified circuit arrangement.

The fiatiron involves the usual soleplate ID. This soleplate is provided with a recessed or channeled area II for accommodation of a suit able heating element I2. A pressure plate I3 is positioned above the heating element I2 and forces the latter firmly against the bottom of the channels II in the soleplate in order that these parts may be held in good heat conductive relation. Clamping screws I4 hold the pressure plate against the heating element and soleplate.

The heating element I2 includes two resistance ribbons I5 and I6 which are wound in parallel spirals on the respective insulating sheets of the heating element. Resistance I5 is provided with terminals IT and I8 at its respective ends, while heating element I6 has corresponding terminals I9 and 2I respectively. A bridging contact 22 connects the terminals I8 and 2| of resistances I5 and I6 at one end. Thus terminals I! and I9 constitute first and second leads at the extreme ends of the combined heating element consisting of individual resistance elements I5 and I6, while terminal I8 constitutes a third lead at the intermediate point between portions I 5 and I6.

Along the central longitudinal line of soleplate ID a recess or channel 23 is provided. Holes 24' in the bottom of channel 23 at the forward end thereof are designed to accommodate retaining pins 26 for a thermostatic control element or bar 25. Pins 26 hold the forward end of thermostat 25 firmly against the bottom of channel 23 so that the thermostat 25 is in good heat conductive relationship with the lower portions of soleplate Ill. Thus the thermostat reflects accurately the heat conditions at the bottom of the soleplate in known manner.

One end of thermostat 25 is provided with an insulating button 21 which engages the downwardly extending arm 28 of switch contact arm 29. The other end 3! of contact arm 29 is adapted to be mounted at 32 on an insulating block 33 fastened to a supporting bracket 34. Bracket 34 is fastened to soleplate I9 by a screw 35.

Since the major portion of thermostat 25 is mounted within channel 23 at a level below the pressure plate I3, and since the contact arm 29 is mounted on insulating block 33 above pressure plate I3, the pressure plate will necessarily be provided with suitable openings (not shown) through which the end 2'! of thermostat 25 may engage the downward projection 28 of the switch arm 29.

One end 33 of a. second switch arm 3! is similarly mounted at 33 on insulating block 33. Switch arms 29 and 31 are provided with cooperating contacts 39 and 4! respectively. The resilience of the switch arms is such that they are normally urged toward each other so'that the contacts 39 and AI will be engaged. However, when the iron reaches a temperature in the range desired for operation, the thermostat 25 will flex upwardly and will lift the switch arm 29 so that contact 39 is separated from contact 4| and the circuit through the thermostatic switch is broken.

The temperature at which this opening of the contacts takes place may be adjusted in known manner by suitable adjustment of the position of switch arm 31. This adjustment is obtained by means of an insulating projection 42 mounted at the lower end of an adjusting rod 43. Rod or shaft 43 is threaded at 44 for engagement with a suitable supporting block (not shown) fastened to the underside of the shell or other structure of the flatiron. A control knob 45 is fastened to the upper end of shaft 43 and is located above the shell 46 of the iron where it is readily accessible to the user. A pointer 47 on control knob 45 cooperates with suitable indicia 48 on the shell 45 or on a suitable index plate fastened to said shell in order to indicate to the user the temperature at which the thermostatic switch is set to operate.

The threads 44 are so arranged that as the knob 45 is rotated in a counterclockwise direction in the figure to the 01f position, the contact arm 31 will be forced downwardly so that contact M is finally separated from contact 39 even when thermostat 25 is in its cold or lower position.

Since the operation of a thermostatic switch of this type and its adjustment are well known to those skilled in the art, no further description thereof will be given. It should be noted that any equivalent form of temperature control switch which is customarily used in the flatiron field may be utilized successfully in the present invention.

Above the shell 45 of the flatiron, a suitable handle 49 is provided. At the rear of this handle an electric supply cord is mounted. This i supply cord is adapted for connection to the usual outlet in the wall of the building in which the flatiron is to be used. The individual conductors 52 and 53 of the supply cord are led downwardly through the handle 49 to the interior of the iron where these wires are connected to suitable terminals 54 and 5", shown only schematically in the drawing.

In order to adapt the iron for selective use with alternating and direct current supplies, a control switch arm 53 is mounted at the end of a rotatable shaft 5'! journaled in the handle 49. Switch arm 53 is insulated from the control shaft 51 in known manner.

A manually operable control knob 58 is fastened to the upper end of shaft 5'! where it is readily accessible to the user. An index mark 59 on handle 49 cooperates with suitable indicia 3i and 32 on knob 58 to indicate to the user the A. C. and D. C. positions of switch arm 56.

Arm 56 carries a contact 63. In the A. C. position of the switch arm 53 as shown in Fig. 1, this contact 33 engages a cooperating fixed contact 64 carried on an insulating block 35 inside the fiatiron. Block- 35 also supports an additional contact 66 which is engaged by contact 63 whenv switch arm 55 and knob 58 are rotated to the D. C. position.

To connect the various parts in electrically op erative relationship, the following circuit is provided.

A wire 3'! connects terminal 55 of supply conductor 53 to the control switch arm 56. A further wire or conductor 68 connects the fixed contact 64 of the control switch to the end 3| of thermostatic switch arm 29. Conductor 69 connects the end 36 of the other thermostatic switch arm 3! to the terminal I8 of heating element ribbon I5. The other terminal ll of heating element ribbon I 5 is connected by wire II to the terminal 54 of supply conductor 52.

The wiring just described completes the circuit for alternating current operation of the iron. In this circuit the current from the supply terminals 54 and 55 passes through the control switch arm 56 through the thermostatic switch contacts 39 and 4! and through the heating element resistance ribbon I5. Since switch contacts 39 and 4| are in series with the element I5, the operation of the thermostatic switch by thermostatic bar 25 will make and break the circuit through the heating element IE to control the operating temperature of the flatiron in known manner.

When the control knob 58 is rotated to the D. C. position so that switch arm 56 engages the contact 65, the circuit from the switch arm will be completed by a wire I2 to terminal I9 of the secondary heating element resistance ribbon I6. In this D. C. position of the control switch, the thermostatic switch contacts 39 and II will no longer be in the circuit, since the circuit is broken at contact 64. Thus, in this case, the circuit from the supply cord 5! will be completed in the. following manner. From supply conductor 53 the current will pass to terminal 55 through wire 61, switch arm 55, contacts 63 and 66, wire I2. terminal I9, resistance element I6, terminal 2I, cross contact 22, terminal I 8, main resistance ribbon I5, terminal I'I, wire II, and terminal 54 back to the other supply conductor 52. thermostatic switch contacts 39 and 4| out of the circuit, there is no possibility of arcing at these contact points. course, bend under the heat conditions of the With the The thermostatic bar 25 will, of:

aosae'ra soleplate' I and will open and close the switch contacts 39 and H, but this operation will have no effect on the electrical circuit itself.

The value of the resistance of the main heat ing element I is so chosen that when the iron is operating in the A. C. circuit, the element I5 will operate at a high wattage. In other words. element I5. when in circuit alone, is capable of producing much more heat than is normally withdrawn from the soleplate II) in normal operation of the iron.

For example, a resistance of substantially 12 ohms for element I5 will give an iron with a rat ing of 1100 watts, when used with 115 volt al. ternating current of the usual household type. The use of this high wattage for A. C. operation is well known and understood and provides an iron which responds quickly to actual ironing conditicns and which tends to maintain even sole plate temperatures under the control or the thermostat and thermostatic switch elements 38 and M.

However, if resistance element I5 were used alone when the iron is operated with a direct current supply, there would be a dangerous tendency for the soleplate III to overheat. It is possible that the resistance I5 might burn out due to the extremely high temperatures which it could reach if the current were not interrupted. Since the thermostatic switch 39, M is not in circuit and cannot interrupt the current to the heating elements, it is accordingly desirable to throw the auxiliary resistance I6 into the circuit for D. C. operation in the manner described.

The value of resistance element IE is such that when elements I5 and- I6 are combined in series as in the direct current circuit, the wet-- tage of the combined resistances will be much reduced. Ina preferred form of the invention the value of this resistance is substantially equal to that of the main heating element. Thus in the specific case above, where element I5 has a resistance of 12 ohms, the use of a similar value for resistance I5 will yield an iron with only half the rating, 1. e., 550 watts.

While this means that the heating of the soleplate I0 will be much slower during direct current operation, this same thing is true in connection with all direct current irons at the present time. Therefore the direct current operation of the present iron is at least as good as that of the direct current travel irons or similar constructions which are now available. At the same time the present construction offers the very great advantages of use with alternating current supplies at higher wattage for improved fiatiron operation whenever such alternating current supplies are available. Thus it is unnecessary for the user to own two irons, one for household use with alternating current and a separate iron for traveling, and for direct current use. The advantages of the two types of irons are combined in a single construction in which it is only necessary to adjust the position of the control knob 58 to utilize the iron selectively with both direct and. alternating current.

In the modified circuit arrangement shown in Fig. 4, the circuit connections are such that the thermal switch designed to control operation of the flatiron on A. C. current is effectively bypassed during D. 0. operation. In this fi ure the parts which are similar to corresponding parts in Fi s. 1 to 3 are given numbers corre sponding to those of the previous figures, but with 100 added. The parts are shown in Fig. 4

in the A. C. position of operation in which the main heating resistance II 5 for flatiron soleplate H0 is connected in series with the thermal switch directly across the current supply terminals on supply lines 52 and 53. This circuit may be traced from supply line 52 through terminal I54, lead III to terminal II I at one end of main heating element II5, thence to terminal H3 at the other end of the main heating element and through lead I69 to terminal I36 at one contact arm I31 of the thermal switch. When contacts I39 and HI of this switch are closed, the circuit is completed through the other switch arm I29, its terminal I3I, lead I68, terminal I", and lead It"! back to the other supply line 53. Movement of thermostat I25 in response to predetermined soleplate temperatures causes engagement oi insulating portion I21 with the down-turned end I28 of contact arm I29 to open and close the switch contacts. Adjusting shaft I43, threaded at I44 and provided with an insulating button I42, controls the position of the other contact arm I31 in the same manner previously described for the first embodiment.

In this modification, the auxiliary resistance I I 6, which is preferably associated with the soleplate as in the previous case, is connected at one end to terminal H8 and has its other terminal H9 connected by lead H4 to one contact I73 of the selective A. C.-D. C. control switch I 55. Arm 112 ci this switch is connected at one end 570 by lead III to terminal 11. The position of switch arm H2 is controlled by shaft I51 and knob I58 having A. C. and D. C. indicia cooperating with the index mark I59 as in the previous cases.

In the A. C. position of Fig. 4, the switch I55 is open and resistance I I6 is out of circuit. When the control knob I58 is moved to the D. C. position, the switch I55 will be closed, so that the switch, together with leads III, I14, and auxiliary resistance IIG will effectively bypass the thermal switch contacts I39 and HI. In this D. C. position, the auxiliary resistance H5 will also be placed. in series with resistance II5 across the supply lines 52 and 53. Passage of current through auxiliary resistance II6 will depend on the position of the thermal switch contacts I39 and MI. In any event, the bypass circuit with its included resistance will substantially prevent arcing at these contact points and will provide a means for continuously energizing the main heating element H5 to a greater or lesser degree. Thus the bypass circuit of Fig. 4 provides a modified arrangement for achieving certain of the objects of the present invention.

Various changes in the specific construction shown in the drawings will be readily apparent to those persons skilled in this art now that applicant has taught the essential features of the present invention. 'Applicant intends to include in his invention all such modifications, changes, and variations as fall within'the spirit and scope of the attached claims.

Now, therefore, I claim:

1. A flatiron for selective automatic and nonautomatic operation comprising a soleplate, a pair 01 electric heating elements operatively associated with the soleplate for heating it, an automatic switch responsive to temperature oi the fiatiron, a pair of terminals for connection to a current supply, and a control switch having a switch arm movable between two positions; means connecting only one of the elements and the automatic switch in series with each. other directly across the terminals when the control switch arm is in one position, and means connecting both of the elements in series with each other directly across the terminals when the control switch arm is in another position.

2. A fiatiron for selective automatic and nonautomatic operation comprising a soleplate, a pair of electric heating elements operatively associated with the soleplate for heating it, an

automatic switch responsive to temperature of the fiatiron, a pair of terminals for connection to a current supply, and a control switch having a switch contact arm movable between two positions; means connecting one of the elements and the automatic switch in series with each other across the terminals when the control switch contact arm is in one position, and means cu ting the automatic switch out of circuit and connecting both of the elements in series with each other across the terminals when the control switch contact arm is in another position.

3. A flatiron for selectivev operation with alternating and direct current comprising a soleplate, an electric heating element operatively associated with the soleplate for heating it and having a first lead at one end, a second lead at the other end, and a third lead connected at an intermediate point on the element, an automatic switch opening and closing in response to temperature changes in the fiatiron, a pair of current supply terminals, a control switch having first and second switch contacts and a main switch arm movable between an A. C. position in which it engages the first contactand a. D. C. position in which it engages the second contact, and an external control knob operatively conconected to the switch arm for movement of the .latter between said positions, one of said supply terminals being connected directly to the first .heating element lead, the other of said supply terminals being connected directly to said switch arm, said automatic switch being connected between said first switch contact and the third heating element lead, and said second switch contact being connected directly to the second heating element lead.

4. A flatiron for selective automatic and nonautomatic operation on alternating and direct current respectively comprising a soleplate, a main electric heating resistance operatively associated with the soleplate for heating it, a thermal switch automatically opening and closing in response to increase and decrease of the temperature of the fiatiron above and below a predetermined range, an auxiliary resistance, a pair of terminals for connection to a current supply, a selective manual control switch having a switch contact arm movable between A. C. and D. C. positions, circuit means connecting only the main resistance and thermal switch in series with each other and directly across the terminals when the control switch contact arm is in its A. C. position, and additional circuit means connecting said main and auxiliary resistances in series with each other and directly across the terminals when the control switch contact arm is in its D. C. position. 5. A flatiron according to claim 4 in which the circuit means also cuts the thermal switch out of circuit when the control switch contact arm is in its D. C. position.

6. A flatiron according to claim 4 in which the auxiliary resistance bypasses the thermal switch when the control switch contact arm is in its D. C. position.

'7. A fiatiron for selective automatic and non-.- automatic operation on alternating and direct current respectively, comprising a soleplate, a main electric resistance element operatively associated with the soleplate for heating it, a thermal switch automatically opening and closing in response to temperature deviations above and below a predetermined fiatiron temperature range to be maintained, a pair of terminals for connection to a current supply, a selective manual control switch having a contact arm movable between A. C. and D. C. positions, circuit means connecting only the main electric resistance element and thermal switch in series with each other directly across the terminals when the control switch contact arm is in its A. C. position, and additional circuit means effectively bypassing the thermal switch and substantially decreasing the heating effect of said main resistance element when the control switch contact arm is in its D. C. position.

8. A flatiron according to claim 4 in which the auxiliary resistance is substantially equal to the main heating resistance.

9. A flatiron according to claim 4 in which the auxiliary resistance is substantially equal to the main heating resistance, and the auxiliary re sistance is operatively associated with the soleplate for transmission of heat to the latter.

10. A flatiron according to claim 4 in which the main heating resistance is substantially 12 ohms.

11. A flatiron for selective automatic and nonautomatic operation, on alternating and direct current respectively, comprising a soleplate, at least two electric resistance elements operatively associated with the soleplate for heating it, a thermal switch automatically opening and closing in response to temperature deviations above and below a predetermined flatiron temperature range to be maintained, a pair of terminals for connection to a current supply, a selective manual control switch having a contact arm movable between A. C. and D. C. positions, circuit means connecting at least one resistance element comprising a predetermined total resistance in series with the thermal switch directly across the terminals when the control switch contact arm is in its A. C. position, and circuit means cutting the thermal switch out of circuit with the terminals and connecting at least one resistance element comprising a greater predetermined total resistance in circuit across the terminals when the control switch contact arm is in its D. C. position.

'12. A flatiron for selective automatic and non- .automatic operation on alternating and direct current respectively, comprising a soleplate, a main electric resistance element operatively associated with the soleplate for heating it, a thermal switch automatically opening and closing in response to temperature deviations above and below a predetermined fiatiron temperature range to be maintained, a pair of terminals for connection to a current supply, a selective manual control switch having a contact arm movable between A. C. and D. C. positions, circuit means connecting only the main electric resistance element and thermal switch in series with each other directly across the terminals when the con trol switch contact arm is in its A. C. position, and circuit means cutting the thermal switch out of circuit with the terminals and continuous ly connecting at least said main resistance element in circuit across the terminals when the 9 control switch contact arm is in its D. C. position.

MAURICE H. GRAHAM.

References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Oca-Balda et a1. Aug. 2, 1921 Morgan Oct. 3, 1922 Nelson et a1 Mar. 25, 1930 10 Nelson et a1. Mar. 25, 1930 Olds Dec. 24, 1935 Braun Sept. 17, 1940 Number Number 

